[WrathWielder]"1) Do you happen to know of a keystroke that will SPLIT (like 'S' does) and then also overlap the 2 events by the default amount in preferences?"

Technically, a Split and then overlap will DO NOTHING. This is because you are dissolving from and to the same video. However, I believe what you are looking for is: Put the cursor on the split position with the event selected and press / on the numeric keypad.

[WrathWielder]"2) Is there a way to join all the frames in an event into a single thumbnail?"

The zoom level will determine the number of frames/pictures you see at once. You can always proceed from frame to frame by using ALT-Arrow.